Integrated Semiconductor Device Including an Electrically Insulative Substrate Under an Electrically Conductive or Semiconductive Heat Spreader and Phase-Change Material (PCM) Radio Frequency (RF) Switches

ABSTRACT

A semiconductor device includes a substrate, an integrated passive device (IPD), and a phase-change material (PCM) radio frequency (RF) switch. The PCM RF switch includes a heating element, a PCM situated over the heating element, and PCM contacts situated over passive segments of the PCM. The heating element extends transverse to the PCM, with a heater line underlying an active segment of the PCM. The PCM RF switch is situated over a heat spreader that is situated over the substrate. The heat spreader and/or the substrate dissipate heat generated by the heating element and reduce RF noise coupling between the PCM RF switch and the IPD. An electrically insulating layer can be situated between the heat spreader and the substrate. In another approach, the PCM RF switch is situated over an RF isolation region that allows the substrate to dissipate heat and that reduces RF noise coupling.

CLAIMS OF PRIORITY

The present application is a continuation-in-part of and claims thebenefit of and priority to application Ser. No. 16/103,490 filed on Aug.14, 2018, titled “Manufacturing RF Switch Based on Phase-ChangeMaterial,” Attorney Docket No. 0150200. The present application is alsoa continuation-in-part of and claims the benefit of and priority toapplication Ser. No. 16/103,587 filed on Aug. 14, 2018, titled “Designfor High Reliability RF Switch Based on Phase-Change Material,” AttorneyDocket No. 0150201. The present application is also acontinuation-in-part of and claims the benefit of and priority toapplication Ser. No. 16/103,646 filed on Aug. 14, 2018, titled “PCM RFSwitch Fabrication with Subtractively Formed Heater,” Attorney DocketNo. 0150202. The present application is further a continuation-in-partof and claims the benefit of and priority to application Ser. No.16/114,106 filed on Aug. 27, 2018, titled “Fabrication of Contacts in anRF Switch Having a Phase-Change Material (PCM) and a Heating Element,”Attorney Docket No. 0150213. The disclosures and contents of all of theabove-identified applications are hereby incorporated fully by referenceinto the present application.

BACKGROUND

Phase-change materials (PCM) are capable of transforming from acrystalline phase to an amorphous phase. These two solid phases exhibitdifferences in electrical properties, and semiconductor devices canadvantageously exploit these differences. Given the ever-increasingreliance on radio frequency (RF) communication, there is particular needfor RF switching devices to exploit phase-change materials. However, thecapability of phase-change materials for phase transformation dependsheavily on how they are exposed to thermal energy and how they areallowed to release thermal energy. For example, in order to transforminto an amorphous phase, phase-change materials may need to achievetemperatures of approximately seven hundred degrees Celsius (700° C.) ormore, and may need to cool down within hundreds of nanoseconds.

In order to rapidly cool down phase-change materials, heat must bedissipated from a PCM RF switch by using heat spreading techniques.However, heat spreaders may pose manufacturing cost and device designchallenges. Further, heat spreaders may result in increased RF noisecoupling which can propagate across a semiconductor device and increaseRF noise experienced by integrated passive devices (IPDs). Techniquesfor reducing RF noise coupling applicable to conventional semiconductordevices may not be suitable for PCM RF switches. Various modificationsin structure can have significant impact on thermal energy managementthat decrease the reliability of PCM RF switches. Accordingly,integrating PCM RF switches with passive devices in the samesemiconductor device can present significant challenges. Specialtymanufacturing is often impractical, and large scale manufacturinggenerally trades practicality for the ability to control devicecharacteristics.

Thus, there is a need in the art for semiconductor devices with improvedheat dissipation for PCM RF switches and reduced RF noise coupling whenPCM RF switches are integrated with passive devices in the samesemiconductor device.

SUMMARY

The present disclosure is directed to substrates and heat spreaders forheat management and RF isolation in integrated semiconductor deviceshaving phase-change material (PCM) radio frequency (RF) switches,substantially as shown in and/or described in connection with at leastone of the figures, and as set forth in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present.

FIG. 2 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application.

FIG. 3 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application.

FIG. 4 illustrates a top view of a portion of a semiconductor devicecorresponding to FIG. 1 according to one implementation of the presentapplication.

FIG. 5 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application.

FIG. 6 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application.

FIG. 7 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 6 according to oneimplementation of the present application.

FIG. 8 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application.

FIG. 9 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 8 according to oneimplementation of the present application.

FIG. 10 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application.

FIG. 11 illustrates a detailed cross-sectional view of a portion of asemiconductor corresponding to FIG. 10 according to one implementationof the present application.

FIG. 12 illustrates a top view of a portion of a semiconductor devicecorresponding to FIG. 10 according to one implementation of the presentapplication.

FIG. 13 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 10 according to oneimplementation of the present application.

DETAILED DESCRIPTION

The following description contains specific information pertaining toimplementations in the present disclosure. The drawings in the presentapplication and their accompanying detailed description are directed tomerely exemplary implementations. Unless noted otherwise, like orcorresponding elements among the figures may be indicated by like orcorresponding reference numerals. Moreover, the drawings andillustrations in the present application are generally not to scale, andare not intended to correspond to actual relative dimensions.

FIG. 1 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application. It is notedthat the term “semiconductor device” in the present application broadlyrefers to a device that might use a semiconductor in one or more layers,or in a substrate, or in parts of the device only. In other words,although a device may include non-semiconductor layers or elements, suchas passive devices, metal layers, dielectrics, or generally elementsthat cannot assume different types and degrees of conductivity assemiconductors do, such a device is still referred to as a“semiconductor device” in the present application due to presence orpotential presence of semiconductors in the device. Despite the factthat in general a device referred to as a “semiconductor device” in thepresent application may include some semiconductor elements, it ispossible that use of semiconductors be minimized or entirely avoided incertain implementations according to the present application.

Semiconductor device 100 includes electrically conductive orsemiconductive substrate 102, electrically insulating layer 104,electrically insulative heat spreader 106, phase-change material (PCM)radio frequency (RF) switch 108, and dielectric 110. It is noted thatdielectric 110 corresponds to multiple dielectric layers and levelscorresponding to a multi-level metallization process as known in theart. The various dielectric layers are shown as single dielectric 110 topreserve focus on the inventive concepts disclosed in the presentapplication. FIG. 1 further illustrates various exemplary integratedpassive devices (IPDs), such as IPD 112 a (shown as resistor 112 a byway of example), IPD 112 b (shown as fuse 112 b by way of example), IPD12 c (shown as capacitor 112 c by way of example), and IPD 112 d (shownas inductor 112 d by way of example), which may be collectively referredto as IPDs 112 in the present application, exemplary metal interconnects114, exemplary vias 116, and exemplary bond pad 118.

Electrically conductive or semiconductive substrate 102 is situatedbelow dielectric 110 and below electrically insulating layer 104.Electrically insulating layer 104 is situated over electricallyconductive or semiconductive substrate 102. Electrically insulative heatspreader 106 is situated over electrically insulating layer 104. PCM RFswitch 108 is situated over electrically insulative heat spreader 106.PCM RF switch 108 utilizes PCM to transfer input RF signals in an ONstate and to block input RF signals in an OFF state. As described below,PCM RF switch 108 requires effective heat dissipation and is a source ofRF noise coupling and/or RF signal interference due to coupling (forexample, capacitive coupling) to neighboring elements and components inthe semiconductor device. For brevity in the present application, theterms RF noise and RF noise coupling are used to generally denotevarious kinds of unwanted RF signals such as, but not limited to, RFsignal interference from neighboring elements and components orinterference from harmonics.

Dielectric 110 is situated over PCM RF switch 108 and over electricallyconductive or semiconductive substrate 102. Dielectric 110 aidsformation and processing of IPDs 112, metal interconnects 114, vias 116,and bond pad 118 in a multi-level metallization. In variousimplementations, dielectric 110 can comprise borophosphosilicate glass(BPSG), tetra-ethyl ortho-silicate (TEOS), silicon oxide (Si_(X)O_(Y)),silicon nitride (Si_(X)N_(Y)), silicon oxynitride (Si_(X)O_(Y)N_(Z)), oranother dielectric.

IPDs 112 are situated in dielectric 110, adjacent to PCM RF switch 108or above PCM RF switch 108. As stated above, dielectric 110 can compriseseveral interlayer metal levels (not shown in FIG. 1) and interlayerdielectrics (not shown in FIG. 1) that provide insulation between theinterlayer metal levels. IPDs 112 and metal interconnects 114 can beformed in the interlayer metal levels, and vias 116 can be formed in theinterlayer dielectrics, all situated adjacent to or above PCM RF switch108.

In the present implementation, IPD 112 a represents a resistor, IPD 112b represents a fuse, IPD 112 c represents a capacitor, such as ametal-oxide-metal (MOM) or a metal-insulator-metal (MIM) capacitor, andIPD 112 d represents an inductor. In various implementations,semiconductor device 100 in FIG. 1 can include more or fewer IPDs thanthose shown in FIG. 1. As described below, the performance of IPDs 112is affected by RF noise coupling in electrically conductive orsemiconductive substrate 102 between PCM RF switch 108 and IPDs 112.

IPD 112 d is coupled to metal interconnects 114 by vias 116. Metalinterconnects, such as metal interconnects 114 can route electricalsignals between IPDs, such as IPD 112 d, and various devices (not shownin FIG. 1). Bond pad 118 is exposed at the top of semiconductor device100 to provide for external connection. Metal interconnects 114, vias116, and bond pad 118 are shown in semiconductor device 100 of FIG. 1 inorder to provide additional context and to better illustrate thatvarious other layers can also exist in a semiconductor device in which aPCM RF switch, such as PCM RF switch 108, may reside. In variousimplementations, semiconductor device 100 in FIG. 1 can include more orfewer metal interconnects, vias, and/or bond pads than shown in FIG. 1.

FIG. 2 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application. Semiconductor device portion120 in FIG. 2 represents the outlined portion 120 in FIG. 1. As shown inFIG. 2, electrically conductive or semiconductive substrate 102 issituated below electrically insulating layer 104. Electricallyconductive or semiconductive substrate 102 can comprise any materialwith low electrical resistivity. In various implementations,electrically conductive or semiconductive substrate 102 is a silicon(Si), germanium (Ge), silicon germanium (Si_(X)Ge_(Y)), silicon carbide(Si_(X)C_(Y)), or group III-V substrate.

Electrically insulating layer 104 is situated over electricallyconductive or semiconductive substrate 102. Electrically insulatinglayer 104 can comprise any material with high electrical resistivity. Invarious implementations, electrically insulating layer 104 is siliconoxide (Si_(X)O_(Y)), silicon nitride (Si_(X)N_(Y)), silicon oxynitride(Si_(X)O_(Y)N_(Z)), or another dielectric. In one implementation, theelectrical resistivity of electrically insulating layer 104 can beapproximately one trillion ohm-meters or greater (>1E12 Ω·m).

Electrically insulative heat spreader 106 is situated over electricallyinsulating layer 104. Electrically insulative heat spreader 106 cancomprise any material with high thermal conductivity and high electricalresistivity. In various implementations, electrically insulative heatspreader 106 can comprise aluminum nitride (Al_(X)N_(Y)), aluminum oxide(Al_(X)O_(Y)), beryllium oxide (Be_(X)O_(Y)), diamond, or diamond-likecarbon. In one implementation, the thermal conductivity of electricallyinsulative heat spreader 106 can range from approximately thirty fivewatts per meter-kelvin to approximately two hundred fifty watts permeter-kelvin (35 W/(m·K)-250 W/(m·K)). In one implementation, theelectrical resistivity of electrically insulative heat spreader 106 canbe approximately one trillion ohm-meters or greater (>1E12 Ω·m).

PCM RF switch 108 is situated over electrically insulative heat spreader106. PCM RF switch 108 utilizes PCM to transfer input RF signals in anON state and to block input RF signals in an OFF state. As describedbelow, PCM RF switch 108 switches between ON and OFF states in responseto crystallizing or amorphizing heat pulses generated by a heatingelement. The PCM must be heated and rapidly quenched in order for PCM RFswitch 108 to switch states. In order to rapidly quench the PCM, heatmust be dissipated from the heating element and from PCM RF switch 108.

Absent the present implementation and in a different approach, PCM RFswitch 108 is situated directly on electrically conductive orsemiconductive substrate 102. Electrically conductive or semiconductivesubstrate 102 may be chosen because it supports common fabricationtechniques and has high thermal conductivity. However, because it iselectrically conductive or semiconductive, it can parasitically coupleto electrically conductive elements of PCM RF switch 108. In turn, RFnoise coupling in electrically conductive or semiconductive substrate102 can propagate across a semiconductor device, such as semiconductordevice 100 in FIG. 1, and increase RF noise experienced by IPDs, such asIPDs 112 in FIG. 1. This RF noise coupling in electrically conductive orsemiconductive substrate 102 between PCM RF switch 108 and IPDs 112decreases the performance of IPDs 112.

In the present implementation, electrically insulative heat spreader 106and electrically insulating layer 104 intervene and provide separationbetween PCM RF switch 108 and electrically conductive or semiconductivesubstrate 102. Because electrically insulative heat spreader 106 hashigh electrical resistivity, it reduces RF noise coupling inelectrically conductive or semiconductive substrate 102 from PCM RFswitch 108. Because electrically insulating layer 104 also has highelectrical resistivity, it further reduces RF noise coupling inelectrically conductive or semiconductive substrate 102 from PCM RFswitch 108. The separation between PCM RF switch 108 and electricallyconductive or semiconductive substrate 102 can be further increased byincreasing the thickness of electrically insulative layer 104 to furtherreduce RF noise coupling. Moreover, because electrically insulative heatspreader 106 has high thermal conductivity, it effectively dissipatesheat generated by PCM RF switch 108.

FIG. 3 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application. In particular, FIG. 3illustrates details of PCM RF switch 108 shown in FIG. 1. As shown inFIG. 3, PCM RF switch 108 is situated over electrically insulative heatspreader 106, which is situated over electrically insulating layer 104,which is situated over electrically conductive or semiconductivesubstrate 102. PCM RF switch 108 includes thermally resistive material122, heater line 124, thermally conductive and electrically insulatinglayer 126, PCM 128 having active segment 130 and passive segments 132,contact dielectric 134, and PCM contacts 136.

Thermally resistive material 122 is situated over electricallyinsulative heat spreader 106, and is adjacent to the sides of heaterline 124. Thermally resistive material 122 extends along the width ofPCM RF switch 108, and is also coplanar with the top of heater line 124.In various implementations, thermally resistive material 122 can have arelative width and/or a relative thickness greater or less than shown inFIG. 3. Thermally resistive material 122 can comprise any material withthermal conductivity lower than that of thermally conductive andelectrically insulating layer 126. In various implementations, thermallyresistive material 122 can comprise Si_(X)O_(Y), Si_(X)N_(Y), or anotherdielectric.

In the present implementation, a segment of thermally resistive material122 is situated between heater line 124 and electrically insulative heatspreader 106. This segment performs as a heat valve. Vertical heatdissipation from heater line 124 is heavily biased toward active segment130 of PCM 128, rather than toward electrically insulative heat spreader106. Thus, active segment 130 of PCM 128 can reach higher temperaturesfor the same applied pulse power. In one implementation, the thicknessof thermally resistive material 122 under heater line 124 isapproximately two hundred angstroms (200 Å). In one implementation,rather than PCM RF switch 108 including a heat valve as a segment ofthermally resistive material 122, PCM RF switch 108 can include a heatvalve distinct from thermally resistive material 122. For example, PCMRF switch 108 can include a liner around heater line 124 that performsas a heat valve. As another example, PCM RF switch 108 can includeanother thermally resistive material under heater line 124 having awidth substantially matching a width of heater line 124. In oneimplementation, a heat valve can be omitted, and heater line 124 can besituated on electrically insulative heat spreader 106.

Heater line 124 is situated in thermally resistive material 122. Heaterline 124 also underlies active segment 130 of PCM 128. Heater line 124generates a crystallizing heat pulse or an amorphizing heat pulse fortransforming active segment 130 of PCM 128. Heater line 124 can compriseany material capable of Joule heating. Preferably, heater line 124comprises a material that exhibits minimal or substantially noelectromigration, thermal stress migration, and/or agglomeration. Invarious implementations, heater line 124 can comprise tungsten (W),molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titaniumtungsten (TiW), tantalum (Ta), tantalum nitride (TaN), nickel chromium(NiCr), or nickel chromium silicon (NiCrSi). For example, in oneimplementation, heater line 124 comprises tungsten lined with titaniumand titanium nitride. Heater line 124 may be formed by a damasceneprocess, a subtractive etch process, or any other suitable process.Heater line 124 can be connected to electrodes of a pulse generator (notshown in FIG. 3) that generates crystallizing or amorphizing voltage orcurrent pulses.

Thermally conductive and electrically insulating layer 126 in FIG. 3 isa sheet situated on top of heater line 124 and thermally resistivematerial 122, and under PCM 128 and, in particular, under active segment130 of PCM 128. Thermally conductive and electrically insulating layer126 ensures efficient heat transfer from heater line 124 toward activesegment 130 of PCM 128, while electrically insulating heater line 124from PCM contacts 136, PCM 128, and other neighboring structures.

Thermally conductive and electrically insulating layer 126 can compriseany material with high thermal conductivity and high electricalresistivity. In various implementations, thermally conductive andelectrically insulating layer 126 can comprise Si_(X)C_(Y), Al_(X)N_(Y),Al_(X)O_(Y), Be_(X)O_(Y), diamond, or diamond-like carbon. In theimplementation illustrated in FIG. 3, thermally conductive andelectrically insulating layer 126 is shown to comprise the same materialas electrically insulative heat spreader 106. However, in otherimplementations, thermally conductive and electrically insulating layer126 and electrically insulative heat spreader 106 can comprise differentmaterials. In one implementation, thermally conductive and electricallyinsulating layer 126 can have a higher thermal conductivity thanelectrically insulative heat spreader 106 to ensure that a heat pulsegenerated by heater line 124 dissipates toward active segment 130 of PCM128 more rapidly than it dissipates toward electrically insulative heatspreader 106. In one implementation, thermally conductive andelectrically insulating layer 126 can be a nugget that does not extendalong the width of PCM RF switch 108. For example, thermally conductiveand electrically insulating layer 126 can be a nugget approximatelyaligned with heater line 124.

PCM 128 is situated on top of thermally conductive and electricallyinsulating layer 126. PCM 128 includes active segment 130 and passivesegments 132. Active segment 130 of PCM 128 approximately overliesheater line 124 and is approximately defined by heater line 124. Passivesegments 132 of PCM 128 extend outward and are transverse to heater line124, and are situated approximately under PCM contacts 136. As usedherein, “active segment” refers to a segment of PCM that transformsbetween crystalline and amorphous phases, for example, in response to acrystallizing or an amorphizing heat pulse generated by heater line 124,whereas “passive segment” refers to a segment of PCM that does not makesuch transformation and maintains a crystalline phase (i.e., maintains aconductive state).

With proper heat pulses and heat dissipation, active segment 130 of PCM128 can transform between crystalline and amorphous phases, allowing PCMRF switch 108 to switch between ON and OFF states respectively. Activesegment 130 of PCM 128 must be heated and rapidly quenched in order forPCM RF switch 108 to switch states. If active segment 130 of PCM 128does not quench rapidly enough, it will not transform and PCM RF switch108 will fail to switch states. How rapidly active segment 130 of PCM128 must be quenched depends on the material, volume, and temperature ofPCM 128. In one implementation, the quench time window can beapproximately one hundred nanoseconds (100 ns) or greater or less.

PCM 128 can be germanium telluride (Ge_(X)Te_(Y)), germanium antimonytelluride (Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), orany other chalcogenide. In various implementations, PCM 128 can begermanium telluride having from forty percent to sixty percent germaniumby composition (i.e., Ge_(X)Te_(Y), where 0.4≤X≤0.6 and Y=1−X). Thematerial for PCM 128 can be chosen based upon ON state resistivity, OFFstate electric field breakdown threshold, crystallization temperature,melting temperature, or other considerations. PCM 128 can be formed, forexample, by physical vapor deposition (PVD), sputtering, chemical vapordeposition (CVD), evaporation, ion beam deposition (IBD), or atomiclayer deposition (ALD). It is noted that in FIG. 3, current flowing inheater line 124 flows substantially under active segment 130 of PCM 128.

Contact dielectric 134 is situated over PCM 128 and over thermallyconductive and electrically insulating layer 126. In variousimplementations, contact dielectric 134 is silicon dioxide (SiO₂),boron-doped SiO₂, phosphorous-doped SiO₂, Si_(X)N_(Y), or anotherdielectric. In various implementations, contact dielectric 134 is alow-k dielectric, such as fluorinated silicon dioxide, carbon-dopedsilicon oxide, or spin-on organic polymer. Contact dielectric 134 can beprovided, for example, by plasma enhanced CVD (PECVD), high densityplasma CVD (HDP-CVD), or spin-on processes.

PCM contacts 136 extend through contact dielectric 134 and connect topassive segments 132 of PCM 128. PCM contacts 136 provide RF signalsto/from PCM 128. In various implementations, PCM contacts 136 cancomprise tungsten (W), aluminum (Al), or copper (Cu).

Because PCM RF switch 108 includes thermally resistive material 122 onthe sides of heater line 124, less heat transfers horizontally (i.e.,from the sides) and more heat dissipates vertically, from heater line124 both toward active segment 130 of PCM 128 and toward electricallyinsulative heat spreader 106. Because electrically insulative heatspreader 106 has high thermal conductivity, it effectively dissipatesthis heat generated by heater line 124. Thus, active segment 130 of PCM128 can rapidly quench and successfully transform phases, and PCM RFswitch 108 can switch states with improved reliability. Additionally,PCM 128 can utilize different materials and different dimensions thatrequire faster quench times.

Because electrically insulative heat spreader 106 has high electricalresistivity, it reduces RF noise coupling in electrically conductive orsemiconductive substrate 102 from PCM contacts 136, PCM 128, and otherneighboring structures in PCM RF switch 108. Accordingly, less RF noisepropagates across semiconductor device 100 (shown in FIG. 1) to IPDs 112(shown in FIG. 1), improving the performance of IPDs 112 and allowingsemiconductor device 100 to be more densely integrated. Becauseelectrically insulating layer 104 also has high electrical resistivity,it further reduces RF noise coupling in electrically conductive orsemiconductive substrate 102 from PCM RF switch 108.

FIG. 4 illustrates a top view of a portion of a semiconductor devicecorresponding to FIG. 1 according to one implementation of the presentapplication. In particular, FIG. 4 illustrates details of a top view ofPCM RF switch 108 shown in FIG. 1. FIG. 3 represents a cross-sectionalview along line “3-3” in FIG. 4. As shown in FIG. 4, PCM RF switch 108includes heating element 140 having heater line 124, terminal segments138, and heater contacts 142. Also shown in FIG. 4 are top views of PCM128, and PCM contacts 136. For purposes of illustration, the top view inFIG. 4 shows selected structures of a semiconductor device. Thesemiconductor device may include other structures not shown in FIG. 4,such as electrically insulative heat spreader 106 (shown in FIG. 3)underlying PCM RF switch 108, and thermally conductive and electricallyinsulating layer 126 (shown in FIG. 3) underlying PCM 128.

Heating element 140 extends along PCM RF switch 108 transverse to PCM128 and, as stated above, includes heater line 124 and terminal segments138. Heater line 124 is approximately centered in heating element 140.Heater line 124 underlies PCM 128. Terminal segments 138 are situated atthe two ends of heating element 140. In the present implementation,terminal segments 138 of heating element 140 are integrally formed withheater line 124 using any materials and processes described above withrespect to heater line 124.

In the present implementation, terminal segments 138 occupy a relativelylarge area so that heating element 140 can generate a crystallizing heatpulse or an amorphizing heat pulse for transforming an active segment ofPCM 128, as described above. For example, electrodes of a voltage orcurrent source (not shown in FIG. 4) large enough to handle acrystallizing current pulse or an amorphizing current pulse withoutsignificant losses can connect to terminal segments 138 of heatingelement 140 by heater contacts 142. In other implementations, terminalsegments 138 may have any other size or shape. In the presentimplementation, three heater contacts 142 are connected to each ofterminal segments 138 of heating element 140. In variousimplementations, more or fewer heater contacts 142 can be used. Invarious implementations, heater contacts 142 can have shapes orarrangements other than those shown in FIG. 4. In variousimplementations, heater contacts 142 can comprise tungsten (W), aluminum(Al), or copper (Cu).

PCM 128 overlies heater line 124 of heating element 140. In response toa crystallizing or an amorphizing heat pulse generated by heatingelement 140, an active segment of PCM 128 can transform from acrystalline phase that easily conducts electrical current to anamorphous phase that does not easily conduct electrical current and,thus, can transform the state of PCM RF switch 108 to an ON state or anOFF state. As described above, electrically insulative heat spreader 106(shown in FIG. 3) is situated under PCM RF switch 108 and dissipatesheat generated by heating element 140. As a result, PCM 128 can rapidlyquench and successfully transform phases, and PCM RF switch 108 canswitch states with improved reliability.

PCM contacts 136 connect to passive segments of PCM 128. PCM contacts136 provide RF signals to and from PCM 128. In various implementations,PCM contacts 136 can comprise tungsten (W), aluminum (Al), or copper(Cu).

FIG. 5 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 1 according to oneimplementation of the present application. FIG. 5 represents across-sectional view along line “5-5” in FIG. 4. As shown in FIG. 5, PCMRF switch 108 is situated over electrically insulative heat spreader106, which is situated over electrically insulating layer 104, which issituated over electrically conductive or semiconductive substrate 102.PCM RF switch 108 includes thermally resistive material 122, terminalsegment 138, contact dielectric 134, and heater contacts 142.Electrically insulative heat spreader 106, electrically insulating layer104, electrically conductive or semiconductive substrate 102, thermallyresistive material 122, terminal segment 138, contact dielectric 134,and heater contacts 142 in FIG. 5 may have any implementations andadvantages described above.

The cross-sectional view in FIG. 5 is similar to the cross-sectionalview in FIG. 3, except for differences noted below. The cross-sectionalview in FIG. 5 does not include PCM 128 or thermally conductive andelectrically insulating layer 126, because line “5-5” in FIG. 4 liesalong terminal segment 138 of heating element 140, which extends outwardand is transverse to PCM 128. Instead of PCM 128 and thermallyconductive and electrically insulating layer 126, contact dielectric 134is situated over terminal segment 138 and thermally resistive material122. Terminal segment 138 in FIG. 5 extends farther along PCM RF switch108 than heater line 124 in FIG. 3, because terminal segment 138occupies a relatively large area. Heater contacts 142 extend throughcontact dielectric 134 and connect to terminal segment 138.

FIG. 6 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application.Semiconductor device 200 in FIG. 6 is similar to semiconductor device100 in FIG. 1, except that semiconductor device 200 in FIG. 6 utilizeselectrically insulative and thermally conductive substrate 202 underelectrically insulative heat spreader 206. Electrically insulative heatspreader 206 is situated over electrically insulative and thermallyconductive substrate 202. PCM RF switch 208 is situated overelectrically insulative heat spreader 206. Notably, semiconductor device200 does not include an electrically insulating layer, such aselectrically insulating layer 104 in FIG. 1, over a substrate. Asdescribed below, semiconductor device 200 in FIG. 6 improves heatdissipation from PCM RF switch 208 and reduces RF noise from PCM RFswitch 208.

FIG. 7 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 6 according to oneimplementation of the present application.

Semiconductor device portion 220 in FIG. 7 represents the outlinedportion 220 in FIG. 6. As shown in FIG. 7, electrically insulative andthermally conductive substrate 202 is situated below electricallyinsulative heat spreader 206. Electrically insulative and thermallyconductive substrate 202 can comprise any material with high thermalconductivity and high electrical resistivity. In variousimplementations, electrically insulative and thermally conductivesubstrate 202 can comprise Al_(X)N_(Y), Al_(X)O_(Y), Be_(X)O_(Y),diamond, or diamond-like carbon. In one implementation, the thermalconductivity of electrically insulative and thermally conductivesubstrate 202 can range from approximately thirty five watts permeter-kelvin to approximately two hundred fifty watts per meter-kelvin(35 W/(m·K)-250 W/(m·K)). In one implementation, the electricalresistivity of electrically insulative and thermally conductivesubstrate 202 can be approximately one trillion ohm-meters or greater(>1E12 Ω·m).

Electrically insulative heat spreader 206 is situated over electricallyinsulative and thermally conductive substrate 202. Electricallyinsulative heat spreader 206 in FIG. 7 can comprise any materialsdescribed above with respect to electrically insulative heat spreader106 in FIG. 2. In the implementation illustrated in FIG. 7, electricallyinsulative and thermally conductive substrate 202 comprises the samematerial as electrically insulative heat spreader 206. However, in otherimplementations, electrically insulative and thermally conductivesubstrate 202 and electrically insulative heat spreader 206 can comprisedifferent materials. In one implementation, electrically insulative heatspreader 206 can have a higher thermal conductivity than electricallyinsulative and thermally conductive substrate 202.

In the present implementation, because electrically insulative heatspreader 206 has high electrical resistivity, it reduces RF noisecoupling from PCM RF switch 208. Because electrically insulative andthermally conductive substrate 202 also has high electrical resistivity,it further reduces RF noise coupling from PCM RF switch 208.Accordingly, an insulating layer, such as electrically insulating layer104 in FIG. 2, is not needed. PCM RF switch 208 can be situated closerto electrically insulative and thermally conductive substrate 202.

Because electrically insulative heat spreader 206 has high thermalconductivity, it effectively dissipates heat generated by PCM RF switch208. Because electrically insulative and thermally conductive substrate202 also has high thermal conductivity, it further dissipates heatgenerated by PCM RF switch 208. Electrically insulative and thermallyconductive substrate 202 also has large mass (shown in FIG. 6), whichdissipates heat more efficiently. Because electrically insulative andthermally conductive substrate 202 is situated on the bottom of thesemiconductor device in FIG. 7, when the semiconductor device is mountedon a printed circuit board (PCB) (not shown in FIG. 7), electricallyinsulative and thermally conductive substrate 202 can further dissipateheat utilizing the PCB. Accordingly, the semiconductor device in FIG. 7will dissipate heat more effectively than the semiconductor device inFIG. 2 that uses electrically insulative heat spreader 106 alone.

FIG. 8 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present. Semiconductor device 300in FIG. 8 is similar to semiconductor device 200 in FIG. 6, except thatsemiconductor device 300 in FIG. 8 utilizes electrically insulativesubstrate 302 under electrically conductive or semiconductive heatspreader 306. Electrically conductive or semiconductive heat spreader306 is situated over electrically insulative substrate 302. PCM RFswitch 308 is situated over electrically conductive or semiconductiveheat spreader 306. Notably, semiconductor device 300 does not include anelectrically insulating layer, such as electrically insulating layer 104in FIG. 1, over a substrate. As described below, semiconductor device300 in FIG. 8 improves heat dissipation from PCM RF switch 308 andreduces RF noise from PCM RF switch 308.

FIG. 9 illustrates a cross-sectional view of a portion of asemiconductor device corresponding to FIG. 8 according to oneimplementation of the present application. Semiconductor device portion320 in FIG. 9 represents the outlined portion 320 in FIG. 8. As shown inFIG. 9, electrically insulative substrate 302 is situated belowelectrically conductive or semiconductive heat spreader 306.Electrically insulative substrate 302 can comprise any material withhigh electrical resistivity. Electrically insulative substrate 302 mayor may not be thermally conductive. In one implementation, electricallyinsulative substrate 302 comprises glass and is not thermallyconductive. In other implementations, electrically insulative substrate302 can comprise Al_(X)N_(Y), Al_(X)O_(Y), Be_(X)O_(Y), diamond, ordiamond-like carbon, and is thermally conductive. In one implementation,the electrical resistivity of electrically insulative substrate 302 canbe approximately one trillion ohm-meters or greater (>1E12 Ω·m).

Electrically conductive or semiconductive heat spreader 306 is situatedover electrically insulative substrate 302. Electrically conductive orsemiconductive heat spreader 306 can comprise any material with lowelectrical resistivity. In various implementations, electricallyconductive or semiconductive heat spreader 306 can comprise Si, Ge,Si_(X)Ge_(Y), or Si_(X)C_(Y). In one implementation, the thermalconductivity of electrically conductive or semiconductive heat spreader306 can range from approximately one hundred fifty watts permeter-kelvin to approximately three hundred seventy watts permeter-kelvin (150 W/(m·K)-370 W/(m·K)).

In the present implementation, because electrically conductive orsemiconductive heat spreader 306 has low electrical resistivity, it maycouple RF noise from PCM RF switch 308. However, because electricallyinsulative substrate 302 has high electrical resistivity, it reduces theRF noise coupling from PCM RF switch 308. Accordingly, less RF noisepropagates across semiconductor device 300 (shown in FIG. 8) to IPDs.

Because electrically conductive or semiconductive heat spreader 306 hashigh thermal conductivity, it effectively dissipates heat generated byPCM RF switch 308. Additionally, electrically conductive orsemiconductive heat spreader 306 in FIG. 9 is generally better attransferring heat. In particular, heat generally transfers faster inmonocrystalline materials than in amorphous materials. For example,electrically insulative heat spreader 206 in FIG. 7 can be amorphousAl_(X)N_(Y), and its thermal conductivity can range from approximatelythirty five watts per meter-kelvin to approximately fifty watts permeter-kelvin (35 W/(m·K)-120 W/(m·K)). In contrast, for example,electrically conductive or semiconductive heat spreader 306 in FIG. 9can be monocrystalline Si, and its thermal conductivity can beapproximately one hundred seventy watts per meter-kelvin (170 W/(m·K)).Where electrically insulative substrate 302 also has high thermalconductivity, it further dissipates heat generated by PCM RF switch 308.

FIG. 10 illustrates a cross-sectional view of a semiconductor deviceaccording to one implementation of the present application.Semiconductor device 400 in FIG. 10 is similar to semiconductor device300 in FIG. 8, except that semiconductor device 400 in FIG. 10 utilizesRF isolation region 450 in electrically conductive or semiconductivesubstrate 402, and PCM RF switch 408 is situated over RF isolationregion 450 in electrically conductive or semiconductive substrate 402.Notably, semiconductor device 400 does not include a heat spreader, suchas electrically conductive or semiconductive heat spreader 306 in FIG.8. As described below, semiconductor device 400 in FIG. 10 improves heatdissipation from PCM RF switch 408 and reduces RF noise from PCM RFswitch 408.

FIG. 11 illustrates a detailed cross-sectional view of a portion of asemiconductor corresponding to FIG. 10 according to one implementationof the present application. Semiconductor device portion 420 in FIG. 11represents the outlined portion 420 in FIG. 10. FIG. 11 illustratesdetails of RF isolation region 450 and PCM RF switch 408 shown in FIG.10.

As shown in FIG. 11, PCM RF switch 408 is situated over RF isolationregion 450 of electrically conductive or semiconductive substrate 402.Electrically conductive or semiconductive substrate 402 can comprise anymaterial with low electrical resistivity. In various implementations,electrically conductive or semiconductive substrate 402 is a Si, Ge,Si_(X)Ge_(Y), Si_(X)C_(Y), or group III-V substrate.

RF isolation region 450 includes shallow trench insulations (STIs) 452,deep trenches 454, insulated portions 456 of electrically conductive orsemiconductive substrate 402, and exposed portion 458 of electricallyconductive or semiconductive substrate 402. It is noted that the STIregions may instead be implemented as LOCOS (local oxidation of silicon)insulation, poly-buffered LOCOS insulation, or any other technique orstructure for substrate isolation where the semiconductor device ispatterned into regions of dielectric (for example, silicon oxide) andsemiconductor (for example, silicon). However, in the presentimplementation, the relative planarity of the STI technique andstructure can be beneficial.

STIs 452 extend into electrically conductive or semiconductive substrate402 from its top surface. STIs 452 primarily reduce RF noise fromcoupling directly between PCM RF switch 408 and electrically conductiveor semiconductive substrate 402. STIs 452 can comprise, for example,silicon dioxide (SiO₂). In one implementation, the depth of STIs 452 canbe approximately half a micron (0.5 μm). Deep trenches 454 extendthrough STIs 452, and into electrically conductive or semiconductivesubstrate 402. Deep trenches 454 primarily reduce RF noise frompropagating across electrically conductive or semiconductive substrate402. Deep trenches 454 can likewise comprise, for example, SiO₂. In oneimplementation, the depth of STIs 452 can be approximately seven microns(7 μm). In the implementation illustrated in FIG. 11, RF isolationregion 450 is shown to include both STIs 452 and deep trenches 454.However, in other implementations, RF isolation region 450 can includeonly STIs 452, or only deep trenches 454. In various implementations, RFisolation region 450 can utilize locally oxidized silicon (LOCOS)instead of or in addition to STIs 452 and deep trenches 454.

Insulated portions 456 are any portions of electrically conductive orsemiconductive substrate 402 insulated by STIs 452 and deep trenches454. Insulated portions 456 are situated approximately under passivesegments 432 of PCM 428 and extend outward away from heater line 424.Insulated portions 456 provide electrical isolation between PCM RFswitch 408 and electrically conductive or semiconductive substrate 402so as to reduce RF noise coupling in electrically conductive orsemiconductive substrate 402 between PCM RF switch 408 and IPDs (shownin FIG. 10).

Exposed portion 458 is a portion of electrically conductive orsemiconductive substrate 402 that is not insulated at its top surface.STIs 452 and deep trenches 454 approximately surround exposed portion458 of electrically conductive or semiconductive substrate 402. Exposedportion 458 is situated under heater line 424 and active segment 430 ofPCM 428. Exposed portion 458 allows electrically conductive orsemiconductive substrate 402 to dissipate heat generated by heater line424. In various implementations, exposed portion 458 may be wider ornarrower than shown in FIG. 11.

Notably, the semiconductor device in FIG. 11 does not include adedicated heat spreader, such as electrically insulative heat spreader106 in FIG. 3, because RF isolation region 450, and particularly exposedportion 458, allows electrically conductive or semiconductive substrate402 to dissipate heat generated by heater line 424. In thisimplementation, thermally resistive material 422 under heater line 424performing as a heat valve also prevents heater line 424 from shortingto electrically conductive or semiconductive substrate 402.

FIG. 12 illustrates a top view of a portion of a semiconductor devicecorresponding to FIG. 10 according to one implementation of the presentapplication. In particular, FIG. 12 illustrates details of PCM RF switch408 shown in FIG. 10. FIG. 11 represents a cross-sectional view alongline “11-11” in FIG. 12. For purposes of illustration, the top view inFIG. 12 shows selected structures of a semiconductor device. Thesemiconductor device may include other structures not shown in FIG. 12,such as a thermally conductive and electrically insulating layerunderlying PCM 428.

As shown in FIG. 12, PCM RF switch 408 is situated over RF isolationregion 450. In RF isolation region 450, exposed portion 458 is situatedunder heater line 424 of heating element 440. As described above,exposed portion 458 dissipates heat generated by heater line 424 ofheating element 440. In various implementations, exposed portion 458 mayhave any sizes or shapes other than those shown in FIG. 12.

In RF isolation region 450, insulated portion 456 surrounds exposedportion 458. As described above, insulated portion 456 provideselectrical isolation from PCM RF switch 408. Notably, in FIG. 12,insulated portion 456 is situated under terminal segments 438 of heatingelement 440 and under heater contacts 442. Because heater contacts 442themselves can be a source of RF noise, for example, due to parasiticcoupling with PCM contacts 436, insulated portion 456 situated underheater contacts 442 can further reduce RF noise coupling from PCM RFswitch 408.

FIG. 13 illustrates a detailed cross-sectional view of a portion of asemiconductor device corresponding to FIG. 10 according to oneimplementation of the present application. FIG. 13 represents across-sectional view along line “13-13” in FIG. 12. As shown in FIG. 13,PCM RF switch 408 is situated over RF isolation region 450 ofelectrically conductive or semiconductive substrate 402.

The cross-sectional view in FIG. 13 is similar to the cross-sectionalview in FIG. 5, except for differences noted below. The cross-sectionalview in FIG. 13 includes RF isolation region 450 situated under PCM RFswitch 408. As shown in FIG. 13, in RF isolation region 450, STI 452 anddeep trenches 454 extend along the length of the semiconductor device.Thus, insulated portion 456 is situated under terminal segment 438 andunder heater contacts 442.

Semiconductor devices according to the present application provide meansfor effectively dissipating heat generated by a heating element of a PCMRF switch, while also reducing RF noise coupling in a substrate betweenthe PCM RF switch and IPDs. Ensuring effective heat dissipation improvesquench times of PCM, and increases the reliability of the PCM RF switch.Reducing RF noise coupling improves the performance of IPDs, and allowsfor more densely integrated semiconductor devices.

Thus, various implementations of the present application achievesemiconductor devices with improved heat dissipation for PCM RF switchesand reduced RF noise coupling for integrated devices that overcome thedeficiencies in the art. From the above description it is manifest thatvarious techniques can be used for implementing the concepts describedin the present application without departing from the scope of thoseconcepts. Moreover, while the concepts have been described with specificreference to certain implementations, a person of ordinary skill in theart would recognize that changes can be made in form and detail withoutdeparting from the scope of those concepts. As such, the describedimplementations are to be considered in all respects as illustrative andnot restrictive. It should also be understood that the presentapplication is not limited to the particular implementations describedabove, but many rearrangements, modifications, and substitutions arepossible without departing from the scope of the present disclosure.

1-9. (canceled) 10: A semiconductor device including an electrically insulative substrate, said semiconductor device further comprising: at least one integrated passive device (IPD); a phase-change material (PCM) radio frequency (RF) switch comprising: a heating element; a PCM situated over said heating element; PCM contacts situated over passive segments of said PCM; said heating element extending transverse to said PCM, a heater line of said heating element approximately underlying an active segment of said PCM; said at least one IPD situated adjacent to or above said PCM RF switch in said semiconductor device; said PCM RF switch being situated over an electrically conductive or semiconductive heat spreader, said electrically conductive or semiconductive heat spreader dissipating heat generated by said heating element, wherein said electrically conductive or semiconductive heat spreader is situated over said electrically insulative substrate; said electrically insulative substrate reducing RF noise coupling between said PCM RF switch and said at least one IPD. 11: The semiconductor device of claim 10, wherein said at least one IPD is selected from the group consisting of a resistor, a capacitor, an inductor, and a fuse. 12: The semiconductor device of claim 10, wherein said electrically conductive or semiconductive heat spreader comprises material selected from the group consisting of silicon (Si) and silicon carbide (Si_(X)C_(Y)). 13: The semiconductor device of claim 10, wherein said electrically insulative substrate comprises material selected from the group consisting of glass, aluminum nitride (Al_(X)N_(Y)), aluminum oxide (Al_(X)O_(Y)), beryllium oxide (Be_(X)O_(Y)), diamond, and diamond-like carbon. 14-20. (canceled) 21: The semiconductor device of claim 10, wherein said PCM comprises material selected from the group consisting of germanium telluride (Ge_(X)Te_(Y)), germanium antimony telluride (Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any other chalcogenide. 22: The semiconductor device of claim 10, wherein said heater line comprises material selected from the group consisting of tungsten (W), molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), tantalum nitride (TaN), nickel chromium (NiCr), and nickel chromium silicon (NiCrSi). 23: A semiconductor device including an electrically insulative substrate, said semiconductor device further comprising: at least one integrated passive device (IPD); a phase-change material (PCM) radio frequency (RF) switch comprising: a heating element; a PCM situated over said heating element; a heater line of said heating element approximately underlying said PCM; said at least one IPD situated adjacent to or above said PCM RF switch in said semiconductor device; said PCM RF switch being situated over an electrically conductive or semiconductive heat spreader, said electrically conductive or semiconductive heat spreader dissipating heat generated by said heating element, wherein said electrically conductive or semiconductive heat spreader is situated over said electrically insulative substrate; said electrically insulative substrate reducing RF noise coupling between said PCM RF switch and said at least one IPD. 24: The semiconductor device of claim 23, wherein said at least one IPD is selected from the group consisting of a resistor, a capacitor, an inductor, and a fuse. 25: The semiconductor device of claim 23, wherein said electrically conductive or semiconductive heat spreader comprises material selected from the group consisting of silicon (Si) and silicon carbide (Si_(X)C_(Y)). 26: The semiconductor device of claim 23, wherein said electrically insulative substrate comprises material selected from the group consisting of glass, aluminum nitride (Al_(X)N_(Y)), aluminum oxide (Al_(X)O_(Y)), beryllium oxide (Be_(X)O_(Y)), diamond, and diamond-like carbon. 27: The semiconductor device of claim 23, wherein said PCM comprises material selected from the group consisting of germanium telluride (Ge_(X)Te_(Y)), germanium antimony telluride (Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any other chalcogenide. 28: The semiconductor device of claim 23, wherein said heater line comprises material selected from the group consisting of tungsten (W), molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), tantalum nitride (TaN), nickel chromium (NiCr), and nickel chromium silicon (NiCrSi). 29: A semiconductor device including an electrically insulative substrate, said semiconductor device further comprising: at least one integrated passive device (IPD); a phase-change material (PCM) radio frequency (RF) switch comprising: a heating element; a PCM situated over said heating element; a heater line of said heating element approximately underlying said PCM; said PCM RF switch being situated over an electrically conductive or semiconductive heat spreader; said electrically conductive or semiconductive heat spreader is situated over said electrically insulative substrate. 30: The semiconductor device of claim 29, wherein said at least one IPD is selected from the group consisting of a resistor, a capacitor, an inductor, and a fuse. 31: The semiconductor device of claim 29, wherein said electrically conductive or semiconductive heat spreader comprises material selected from the group consisting of silicon (Si) and silicon carbide (Si_(X)C_(Y)). 32: The semiconductor device of claim 29, wherein said electrically insulative substrate comprises material selected from the group consisting of glass, aluminum nitride (Al_(X)N_(Y)), aluminum oxide (Al_(X)O_(Y)), beryllium oxide (Be_(X)O_(Y)), diamond, and diamond-like carbon. 33: The semiconductor device of claim 29, wherein said PCM comprises material selected from the group consisting of germanium telluride (Ge_(X)Te_(Y)), germanium antimony telluride (Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any other chalcogenide. 34: The semiconductor device of claim 29, wherein said heater line comprises material selected from the group consisting of tungsten (W), molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), tantalum nitride (TaN), nickel chromium (NiCr), and nickel chromium silicon (NiCrSi). 